Abstract:
The lower basin of Kelani River, encompassing
the highly populated Colombo metropolitan area, frequently
suffers severe inundation due to high river discharges and
localized heavy rainfall. This research utilized the HEC-RAS
2D model to analyze water levels in the Kelani River, assess
flood extents, and make reliable future predictions despite
limited data availability The model was calibrated and
validated by comparing observed and simulated water levels
during the May 2008 and June 2016 flood events,
demonstrating satisfactory performance with a Root Mean
Square Error of 0.134 m, coefficient of correlation of 0.951,
Nash-Sutcliffe efficiency of 0.914, and a goodness-of-fit index of
70.1% for inundation extents. Additionally, an ArcGIS model
was employed to generate a flood susceptibility map for the
lower basin of the Kelani River. The study included identifying
flood-prone areas in Colombo suburbs, assessing the flood risk
through simulating hypothetical flood bund breaches,
estimating the flood extent, evaluating the efficiency of existing
flood bunds, and assessing the vulnerability of areas protected
by flood bunds on the left bank of Kelani River during 50- and
100-year Kelani floods and a 50-year rainfall in Colombo
metropolitan area. This analysis provides valuable insights into
the potential advantages of investing in infrastructure
improvements to mitigate flood risk in the Colombo Suburbs.
Citation:
P. G. T. N. Geeshan, T. M. N. Wijayaratne and J. M. A. S. S. Jayasundara, "Vulnerability of Colombo Suburbs for Kelani River Floods," 2023 Moratuwa Engineering Research Conference (MERCon), Moratuwa, Sri Lanka, 2023, pp. 143-148, doi: 10.1109/MERCon60487.2023.10355474.